Some time ago Nvidia offer AMD, to use GPU accelerated Physx via CUDA. Now it seems like AMD accepted the offer.
AMD HD 4870: Going to be a physics accelerator soon?
Quelle: PC Games Hardware
This is what Overclock3D.com reports - accordingly AMD is going to accelerate physics calculations, as Nvidia is doing with the beta driver 177.39 already, in the future. Although it will take AMD a little longer to deliver an appropriate driver, but it is said to be just a matter of time.
This could result in a comfortable position for AMD, who could use both Havok and Physx: they got licenses for both solutions.